This invention relates to a data collector for use with a scintillation camera employed in medical diagnosis or the like and more particularly to such a data collector capable of converting the size of the collection matrix of an image memory for collecting distribution image data and the conversion of many like kinds of collecting matrices.
As shown in FIG. 2, a conventional scintillation camera may be used to detect the distribution of a radioisotope injected in a body, for instance, the human body, using a radiation detector 1, collect the distribution image data in an image memory of a data collector 3 by means of the control of a CPU (Central Processing Unit) 2 and display the distribution image on a display unit 4 such as a cathode-ray tube.
The conventional data collector 3 comprises, as shown in FIG. 3, X- and Y-direction A/D converters 5, 5', converter switches S.sub.1 -S.sub.3, S.sub.1 '-S.sub.3 ', an X address register 6 and a Y address register 6', a two-dimensional image memory 7 and an increment circuit 8. The radiation detector 1 detects radiations such as .gamma. rays emitted from an object being examined and produces position signals x, y simultaneously with an unblanking signal u indicating that the incident .gamma. ray has a predetermined amount or more of energy, the position signals x, y being held and respectively converted into digital signals by the A/D converters 5, 5' when the unblanking signal u is applied thereto. The X- and Y-direction position data Dx, Dy are respectively applied to X address register 6 and Y address register 6' of the large memory 7, which has a two-dimensional collection matrix, through the converter switches S.sub.1 -S.sub.3, S.sub.1 '-S.sub.3 '. The distribution image data is then collected in the image memory 7 by reading out the data in the memory location determined by the addresses stored in registers 6, 6', using increment circuit 8 to add one to the data that has been read out, and then writing the incremented data back to the same address determined by the contents of registers 6, 6'.
In the above collection of distribution image data, conversion of the size of the collection matrix is implemented by effectively rendering the distribution image data coarse. That is, it sometimes is necessary to decrease the capacity of image memory 7 so that a plurality of distribution images may be collected in image memory 7. This size conversion of the collection matrix has heretofore been carried out as follows. As shown in FIG. 4 (the X direction only will be described), assuming the output of A/D converter 5 is, for instance, set at 6 bits (2.sup.0 -2.sup.5), position data Dx is applied to X address register 6, which has six address bits (2.sup.0 -2.sup.5), through one of the three converter switches S.sub.1 -S.sub.3.
The first converter switch S.sub.1 is operated when image memory 7 is to be completely filled with the collected data. Assuming the two-dimensional collection matrix of the image memory 7 is a 64.times.64 matrix, the output of 6 bits (2.sup.0 -2.sup.5) of A/D converter 5 is applied to the six address bits (2.sup.0 -2.sup.5) of X address register 6 at a 1:1 ratio. When a 32.times.32 matrix is used for data collection in a 1/4 area of image memory 7, second converter switch S.sub.2 is operated to connect the output of the upper rank 5 bits (2.sup.1 -2.sup.5) of the A/D converter 5 with the lower rank 5 bits (2.sup.0 -2.sup.4) of X address register 6 at a 1:1/2 ratio. Moreover, when a 16.times.16 matrix is used for data collection in a 1/16 area of the image memory, the third converter switch S.sub.3 is operated to connect the output of the upper rank 4 bits (2.sup.2 -2.sup.5) with the lower rank 4 bits of X address register 6 at a 1:1/4 ratio. Similar connections are provided in the Y direction through the converter switches S.sub.1 '-S.sub.3 '. Unchanged, 1/2 or 1/4 conversion has thus been applied to the collection matrix of image memory 7.
In the conventional data collector, however, the size conversion of the collection matrix requires the above converter switches for effecting the conversion ratio. Accordingly, a number of converter switches are present on the address line extending from A/D converters 5, 5' to address registers 6, 6', making the circuit complicated. Moreover, although 1/2, 1/4, 1/8 . . . conversions are possible in each of the X and Y directions, 1/3, 1/5 . . . conversions are unavailable and thus the number of conversion ratios is limited. Furthermore, the polarity of the distribution image data in both the X and Y directions cannot be inverted.